1. Field of the Invention
The present invention relates generally to ink jet recording, and more particularly, to an ink tank for storing ink to be supplied to a recording means which is adapted to discharge the ink for recording; an ink jet head cartridge which has such ink tank and recording means integrated with each other; and an ink jet recording apparatus equipped with the ink jet head cartridge.
2. Related Background Art
An ink jet recording apparatus adapted to discharge ink from discharging orifices thereof for performing desired recording has mounted therein an ink tank for storing ink which is supplied to a recording head for discharging the ink. Such ink tanks may be mainly classified into a type which stores liquid ink as it is in an ink tank housing and a type which stores liquid ink absorbed in an absorptive material in an ink tank housing. In particular, the former type is capable of storing a large amount of liquid ink and is widely utilized because of its relatively high utilizing efficiency of ink. There have been proposed two styles for the ink tank of the type which stores liquid ink as it is. More specifically, one is an ink tank provided with an ink sack for storing ink, and the other one is an ink tank which directly stores ink in space defined between a housing and an air bag, the inside of which communicates with the atmosphere, as described, for example, in Japanese Laid-open Patent Application No. 60-82353. The latter is advantageous over the former in that an inner wall portion of the ink storing housing can be effectively utilized and therefore an ink storing ratio is higher with the outer size being equal.
With the latter style, however, it is difficult to favorably introduce air into the air bag to uniformly inflate same. In other words, an increase of volume of the air bag may lack uniformity depending on an initial condition of the air bag.
Also, since a low rigidity material is used for the air bag to allow a change in volume, if an external shock is applied to the air bag for some reason, the air bag violently swings, which possibly results in inconsistency of ink supply.
The above-mentioned inconsistent increase of volume or swinging movement of ink, if it arises, may cause difficulties in maintaining a favorable ink supply condition from the ink tank to an ink introducing pathway. For example, if an air bag portion positioned on the ink supply side is inflated earlier due to an inconsistent change in volume of the air bag, ink present in the opposite area cannot be favorably introduced to a supply port, thereby possibly causing degradation of the ink utilization efficiency.